System and Method for Routing Using Path Identifiers

ABSTRACT

In one embodiment, a method includes receiving a first packet sent by a first node. The packet includes a first Layer 3 source address, a first Layer 3 destination address, a first Layer 2 source hardware identifier, a first Layer 2 destination hardware identifier, and a first path identifier. The first path identifier is situated between a Layer 2 header of the first packet and a Layer 3 header of the first packet. The method includes automatically determining a first port of the first network element associated with a second node. The second node is associated with the first Layer 2 destination hardware identifier. A second path identifier is automatically determined based on the first port. The first packet is prevented from being delivered to the second node in response to determining that the first path identifier and the second path identifier are different.

TECHNICAL FIELD

This disclosure relates generally to computer networks and moreparticularly to a system and method for routing using path identifiers.

BACKGROUND

In order to provide efficient use of resources and improved reliability,networks are often configured with logical or virtual servers ratherthan a single entity server. For example, enterprise networks often usea logical server to represent multiple physical devices. Also, manynetwork managers are turning to virtualization so that resources can beshared across a network. Through the use of virtualization, multipleoperating systems and applications can run on the same computer at thesame time, thereby increasing utilization and flexibility of hardware.Virtualization allows servers to be decoupled from underlying hardware,thus resulting in multiple virtual servers sharing the same physicalserver hardware. This also allows the virtual server to be moved fromone physical server to another physical server. Using such technology ina data center where multiple service providers are hosted can lead toproblems that have not been adequately addressed. Examples includesecurity issues and resource usage issues.

SUMMARY

In one embodiment, a method executed by at least one processor includesreceiving, at a first network element, a first packet sent by a firstnode. The packet includes a first Layer 3 source address, a first Layer3 destination address, a first Layer 2 source hardware identifier, afirst Layer 2 destination hardware identifier, and a first pathidentifier. The first path identifier is situated between a Layer 2header of the first packet and a Layer 3 header of the first packet. Themethod also includes automatically determining, in response to receivingthe first packet, a first port of the first network element associatedwith a second node. The second node is associated with the first Layer 2destination hardware identifier. The method includes automaticallydetermining a second path identifier based on the first port andautomatically preventing the first packet from being delivered to thesecond node associated with the first Layer 2 destination hardwareidentifier in response to determining that the first path identifier andthe second path identifier are different.

In some embodiments, the first network element may include a switch. Themethod may include determining, at a second network element, the firstpath identifier based on an ingress port of the second network elementconfigured to receive the first packet. The method may also includeinserting, by the second network element, the first path identifier intothe first packet. Inserting the first path identifier into the firstpacket may include adding a header comprising the first path identifierto the first packet.

In one embodiment, a system includes a first network element configuredto receive a first packet sent by a first node. The packet includes afirst Layer 3 source address, a first Layer 3 destination address, afirst Layer 2 source hardware identifier, a first Layer 2 destinationhardware identifier, and a first path identifier. The first pathidentifier is situated between a Layer 2 header of the first packet anda Layer 3 header of the first packet. The first network elementcomprises a processor that is configured to automatically determine afirst port of the first network element associated with a second node inresponse to receiving the first packet. The second node is associatedwith the first Layer 2 destination hardware identifier. The processor isalso configured to automatically determine a second path identifierbased on the first port. The processor is further configured toautomatically prevent the first packet from being delivered to thesecond node associated with the first Layer 2 destination hardwareidentifier in response to determining that the first path identifier andthe second path identifier are different.

Depending on the specific features implemented, particular embodimentsmay exhibit some, none, or all of the following technical advantages.Traffic may be isolated amongst multiple service providers within a datacenter. Services may be moved across hosts in a data center with reducedforwarding latencies. Other technical advantages will be readilyapparent to one skilled in the art from the following figures,description and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference is now made to the following description taken in conjunctionwith the accompanying drawings, wherein like reference numbers representlike parts and which:

FIG. 1 illustrates one embodiment of a system that implements aframework for routing using path identifiers;

FIG. 2 is a table illustrating an example of virtual machines beinghosted on different hosts within a data center at different periods oftime;

FIG. 3 illustrates information that may be stored in a router of FIG. 1;

FIG. 4 illustrates tables that include examples of information that maybe included in switches of FIG. 1;

FIG. 5 is a block diagram illustrating one embodiment of incorporating apath identifier in a packet routed in the system of FIG. 1;

FIG. 6 illustrates an example method for routing a packet using a pathidentifier in the system of FIG. 1; and

FIG. 7 illustrates an example computer system suitable for implementingone or more portions of particular embodiments.

DESCRIPTION OF EXAMPLE EMBODIMENTS

FIG. 1 illustrates one embodiment of system 100 that implements aframework for routing using path identifiers. System 100 includes client110 coupled to network 120. Network 120 is also coupled to data center140. In data center 140, network elements such as router 150 andswitches 160 and 170 are used to network hosts 180-185. One or more ofhosts 180-185 may be used to provide services to client 110 over network120. In some embodiments, virtual machines may be used to provide suchservices. For example, host 180 may include virtual machine VM1 and host181 may include virtual machine VM2. Virtual machines VM1 and VM2 may beused to provide services to client 110. Communication from client 110may be routed to one or more of hosts 180-185 using a path identifierthat is used within data center 140. Border element 130 (another networkelement) may be used to apply path identifiers to communication fromnetwork 120 entering data center 140.

In certain embodiments, multiple service providers may utilize theresources of data center 140 to provide services to clients. In suchembodiments, the path identifiers may reduce or eliminate routing,security, or other challenges that arise in such an environment. Inparticular embodiments, the path identifiers prevent communications frombeing routed to particular interfaces or ports. For example, a networkentity of data center 140 may determine whether to forward a packetalong a particular network path based on the path identifier of thepacket and may drop the packet if the path identifier is invalid. Insuch embodiments, path identifiers may prevent one service or vendorfrom sending packets to another service or vendor in data center 140.This may prevent one service or vendor from being able to observeInternet Protocol (IP) addresses associated with another service orvendor in data center 140. As another example, the use of pathidentifiers may allow for a logical division of a network in data center140 to occur. This enables hardware to be divided into groups. This mayallow for dynamic reassignment of hardware resources and associatedefficiencies (e.g., being able to power off hardware when it is not inuse).

In particular embodiments, a path identifier is situated between a layer2 header and a layer 3 header of a packet. Such embodiments may allowfor a greater number of unique path identifiers (and thus mayaccommodate a greater number of services or service providers) than apath identifier placed in a constrained space such as a layer 2 header.In various embodiments, the path identifier is added to a packet by anetwork element of data center 140 and the packet is delivered (orprevented from being delivered) without swapping or changing the pathidentifier during routing of the packet. In particular embodiments, thepath identifier is used (in combination with other information) todetermine the route a packet should take. In other embodiments, the pathidentifier is decoupled from the routing procedure. That is, in suchembodiments, the path identifier is not taken into account to determinethe path that a packet should take when the packet is routed to thedestination of the packet. Rather, the path of the packet is decidedusing different means, and the path identifier is utilized to determinewhether the packet may be forwarded along that path. Thus, the routinglogic of a network element may include a logical block (e.g., anapplication-specific integrated circuit (ASIC)) that determines all or aportion of the routing path and a separate logical block (e.g., adifferent ASIC) that performs functions related to the path identifierand other port-related functions.

In some embodiments, client 110 may refer to any device that enables auser to interact with one or more services provided in data center 140using network 120. In some embodiments, client 110 may include acomputer, workstation, telephone, Internet browser, electronic notebook,Personal Digital Assistant (PDA), computer tablet, or any other suitabledevice (wireless, wireline, or otherwise), component, or element capableof receiving, processing, storing, or communicating information withother components of system 100. In some embodiments, for example, client110 may be a smartphone, a desktop computer, a laptop computer, or anIP-enabled telephone. Client 110 may also comprise any suitable userinterface such as a display. System 100 may include any suitable numberof clients such as client 110 that may be operated by any suitablenumber of users.

Network 120, in some embodiments, may be implemented using one or morenetworks, such as an ad hoc network, a personal area network (PAN), alocal area network (LAN), a wide area network (WAN), a metropolitan areanetwork (MAN), or one or more portions of the Internet. One or moreportions of one or more of these networks may be wired or wireless. Asexamples, network 120 may be implemented using one or more of a wirelessPAN (WPAN) (e.g., a BLUETOOTH WPAN), a WI-FI network, a WI-MAX network,a Long Term Evolution (LTE) network, a cellular telephone network (e.g.,a Global System for Mobile Communications (GSM) network), or othersuitable wireless network.

In some embodiments, border element 130, router 150, switches 160,and/or hosts 180-185 may each be implemented using one or more computingsystems. Software running on one or more of such computing systems mayperform one or more steps of one or more methods described orillustrated herein or provides functionality described or illustratedherein. Such computing systems may be in any suitable physical form. Asexamples and not by way of limitation, a computing system may be avirtual machine (VM), an embedded computer system, a system-on-chip(SOC), a single-board computer system (SBC) (e.g., a computer-on-module(COM) or system-on-module (SOM)), a desktop computer system, a laptop ornotebook computer system, an interactive kiosk, a mainframe, a mesh ofcomputer systems, a server, an application server, a router, a switch,or a combination of two or more of these. Where appropriate, computingsystems may: be unitary or distributed; span multiple locations; spanmultiple machines; or reside in a computing cloud (e.g., a networked-setof computing systems), which may include one or more cloud components inone or more networks. Where appropriate, one or more computing systemsmay perform without substantial spatial or temporal limitation one ormore steps of one or more methods described or illustrated herein. As anexample and not by way of limitation, one or more computing systems mayperform in real time or in batch mode one or more steps of one or moremethods described or illustrated herein. One or more computing systemsmay perform at different times or at different locations one or moresteps of one or more methods described or illustrated herein, whereappropriate.

Routing data 132, 152, 162, and 172 may each be implemented using anysuitable structure for storing and retrieving information in someembodiments. Databases, file systems, tables, lists, or suitablecombinations of these structures are examples of how any of routing data132, 152, 162, and 172 may be implemented. Computer-readablenon-transitory storage media may be used to implement any of routingdata 132, 152, 162, and 172, such as: a semiconductor-based or otherintegrated circuit (IC) (e.g., a field-programmable gate array (FPGA) oran application-specific IC (ASIC)), a hard disk, an HDD, a hybrid harddrive (HHD), an optical disc, an optical disc drive (ODD), amagneto-optical disc, a magneto-optical drive, a floppy disk, a floppydisk drive (FDD), magnetic tape, a holographic storage medium, asolid-state drive (SSD), a RAM-drive, a SECURE DIGITAL card, a SECUREDIGITAL drive, another suitable medium, or a suitable combination ofthese, where appropriate. A computer-readable non-transitory storagemedium may be volatile, non-volatile, or a combination of volatile andnon-volatile, where appropriate.

In some embodiments, routing modules 134, 154, 164, and 174 may beimplemented using software, hardware, firmware, or any suitablecombination of the three. Routing modules 134, 154, 164, and 174 mayeach include instructions intended to be executed by a processing deviceto accomplish the functions described herein with respect to borderelement 130, router 150, switch 160, and switch 170, respectively.

Border element 130 may be used to process communication entering orexiting data center 140 in some embodiments. Border element 130 mayperform security functions, such as packet inspection, firewall-relatedactivities, and intrusion detection activities. Border element 130 mayalso perform activities related to path identifiers, such as insertingpath identifiers into packets entering data center 140 and removing pathidentifiers from packets leaving data center 140. The actions discussedherein performed by border element 130 may be performed using routingmodule 134 and information contained in routing data 132. For example,routing data 132 may include information that associates IP addresseswith path identifiers and routing module 134 may use such information toinsert and/or remove path identifiers from packets. As another example,routing data 132 may associate path identifiers with ports (e.g.,ingress ports) of border element 130, and routing module 134 may usesuch information to insert and/or remove path identifiers from packets.

In some embodiments, virtual machines VM1 and VM2 may each be a softwareimplementation of a computing device (e.g., a computer) that executesprograms like a physical computing device. As examples, virtual machinesVM1 and VM2 may each be a platform that supports the execution of acomplete operating system and/or a process virtual machine that isdesigned to run one or more programs. Virtualization solutions fromVMWARE, PARALLELS, and XEN are examples of manners in which virtualmachines VM1 and VM2 may be implemented. Virtual machines VM1 and VM2may each be configured to provide one or more services and may each becapable of executing on one or more of hosts 180-185.

Data center 140 may represent a collection of hardware devices thatserve to host multiple applications used by client 110 using network 120in some embodiments. Data center 140 may include one or more networksthat allow for communication sessions to occur with hosts 180-185.Multiple service providers may use aspects of the infrastructure of datacenter 140 to provide services. For example, a service provider may havean agreement with an entity associated with data center 140 wherein theservice provider may utilize one or more of hosts 180-185 to provide oneor more services. This may be true of other service providers. As aresult, in some embodiments, multiple service providers may utilize thesame hardware resources (e.g., one or more of hosts 180-185) of datacenter 140 or may reside on the same network or sub-network within datacenter 180. Virtualization techniques may be used to provide multipleservice providers access to physical hardware resources of data center140. For example, services by service providers may be implemented usingvirtual machines (e.g., virtual machines VM1 and VM2) hosted on hardwaresuch as hosts 180-185.

In some embodiments, management of hardware resources in data center 140may lead to virtual machines being run on different hardware devicesdepending on the environment and traffic patterns within data center140. As a result, a virtual machine providing a service may be hosted ondifferent ones of hosts 180-185 over time. Such characteristics ofproviding services using data center 140 may lead to challenges that maybe ameliorated using path identifiers. For example, the movement of avirtual machine from one hardware device to another (e.g., virtualmachine VM1 may be hosted on host 180 at one point in time and host 182at another point in time) may cause routing challenges and securitychallenges. As another example, isolating traffic amongst multipleservice providers within data center 140 may be difficult becauseservices of multiple service providers may be offered from hosts thatreside on the same network segment (e.g., one service provider may haveits service hosted on host 180 while a different service provider mayhave a service hosted on host 182). As another example, having theability to move services across hosts in data center 140 may lead toforwarding latencies and scaling issues (e.g., scaling to millions ofvirtual hosts). Fairly sharing the distribution of resources in datacenter 140 amongst multiple service providers can also be a challengethat is partially or fully addressed using path identifiers. Anotherbenefit of using path identifiers is the ability to provide policy-basedforwarding of Ethernet flows.

FIG. 2 is a table illustrating an example of virtual machines VM1 andVM2 being hosted on different hosts within data center 140 at differentperiods of time. At time T1, virtual machine VM1 is hosted on host 180and virtual machine VM2 is hosted on host 181. Virtual machine VM1 maybe associated with a network address such as Internet Protocol (IP)address 1.1.1.1. On host 180 at time T1, virtual machine VM1 may beassociated with a hardware address such as Media Access Control (MAC)address 20-20-1-1-0-0 and virtual machine VM2 at time T1 may beassociated with MAC address 20-20-1-2-0-0 while at host 181. At time T2,virtual machine VM2 is hosted on a different host, host 183. However,virtual machine VM2 will keep its IP address even though it is at adifferent host; hence, the IP address of virtual machine VM2 is 1.1.1.2.Virtual machine VM2 will also be associated with the same pathidentifier (path identifier 2) even though it has changed hosts. The MACaddress associated with virtual machine VM2 may be different becausevirtual machine VM2 is at a different host than at time T1; in variousembodiments, the MAC address may not change. The MAC address of virtualmachine VM2 at time T2 is 20-20-2-2-0-0. At time T3, virtual machine VM1is at a different host than it was at times T1 and T2. As a result, theMAC address associated with virtual machine VM1 may be different:20-20-3-1-0-0; in various embodiments, the MAC address may not change.However, both the IP address and the path identifier associated withvirtual machine VM1 is the same as in time periods T1 and T2. At timeT4, virtual machine VM2 is at a different host (host 185) than at timeT3. Virtual machine VM2 may have a different MAC address than inprevious time periods: 20-20-4-1-0-0. At time T4, though, virtualmachine VM2 has the same path identifier and the same IP address asbefore.

In some embodiments, when a virtual machine moves from one host toanother, aspects of system 100 may be updated to reflect the move. Asexamples, any of routing data 132, 152, 162, and 172 may be updated. MACaddress flooding may be used to update routing data 132, 152, 162, and172 when a virtual machine has moved to another host. For example, ifvirtual machine VM1 moves from host 180 to host 182, one or more ofborder element 130, router 150, and switches 160 and 170 may transmitinformation indicating virtual machine VM1 is now associated with MACaddress 20-20-3-1-0-0. While aspects of the Address Resolution Protocol(ARP) may be used to implement the communication discussed in thisparagraph, any suitable protocol or technique may be used.

FIG. 3 illustrates information that, in some embodiments, may be storedin router 150. The destination IP addresses of packets coming into datacenter 140 may be associated with an interface and a path identifier byrouter 150. For example, router 150 may associate IP address 1.1.1.1with path identifier 1 and IP address 1.1.1.2 with path identifier 2. Ifrouter 150 receives a packet that has a destination IP address of1.1.1.1, router 150 will ensure that the packet also includes pathidentifier 1 before continuing to route the packet to the appropriateswitch over the interface associated with IP address 1.1.1.1 (e.g.,interface ETH 1/1). Similarly, router 150 may ensure that a packetdestined for IP address 1.1.1.2 includes path identifier 2 beforerouting the packet out through interface ETH 1/2. For example, if apacket received by router 150 has a destination IP address of 1.1.1.1,but does not include a path identifier or the path identifier in thepacket is not path identifier 1, then router 150 may not continue toroute the packet (e.g., router 150 may drop the packet). The actionsperformed by router 150 described above may be performed using routingmodule 152.

FIG. 4 illustrates tables 410 and 420 that include examples ofinformation that may be included in switches 160 and 170, respectively.In some embodiments, switch 160 may include information that associatesIP addresses set as the destination address of incoming packets withhardware identifiers (e.g., MAC addresses) and interface ports (e.g.,Ethernet ports). Switch 160 associates IP address 1.1.1.1 with MACaddress 20-20-1-1-0-0 and will route incoming packets for IP address1.1.1.1 onto port ETH 5/1. Switch 170 associates IP address 1.1.1.2 withMAC address 20-20-1-2-0-0 and will route incoming packets for IP address1.1.1.2 onto port ETH 6/1. FIG. 4 illustrates similar types ofinformation being associated with IP addresses 1.0.1.1 and 1.1.1.3 intables 410 and 420. In some embodiments, tables 410 and 420 may alsoassociate the ports of switches 160 and 170 with path identifiers. Forexample, port ETH 5/1 may be associated with path identifier 1 and portETH 5/2 may be associated with path identifier 2. The informationrepresented in table 410 may be stored as routing data 162. Theinformation represented in table 420 may be stored as routing data 172.The actions performed by switch 160 described above may be performedusing routing module 164. The actions performed by switch 170 describedabove may be performed using routing module 174. In some embodiments,service providers using data center 140 may be associated with differentports of switches 160 and/or 170. For example, one service provider maybe associated with interface ETH 5/1 of switch 160 while a separateservice provider may be associated with ETH 5/2 of switch 160. A pathidentifier may be associated with each service provider and each port ofswitches 160 and 170. In some embodiments, this may be provide for aform of network segmentation such that multiple service providers usingresources in data center 140 may have their traffic segmented from eachother.

FIG. 5 is a block diagram illustrating one embodiment of incorporating apath identifier in packet 500 routed in system 100 of FIG. 1. Packet 500includes MAC information 500, IP header 530, and payload 540. Pathidentifier 520 may be a separate layer of packet 500 (e.g., situatedbetween Layer 2 and Layer 3 information in packet 500).

FIG. 6 illustrates an example method for routing a packet using a pathidentifier in system 100 of FIG. 1. The steps of FIG. 6 discussed belowmay be repeated as necessary to route multiple packets. While the stepsof FIG. 6 are discussed below using the components and configuration ofFIG. 1 as an example, the steps of FIG. 6 may be performed in othersuitable manners as discussed further below. Particular embodiments mayrepeat the steps of the method of FIG. 6, where appropriate. Moreover,although this disclosure describes and illustrates particular steps ofthe method of FIG. 6 as occurring in a particular order, this disclosurecontemplates any suitable steps of the method of FIG. 6 occurring in anysuitable order. Furthermore, although this disclosure describes andillustrates particular components, devices, or systems carrying outparticular steps of the method of FIG. 6, this disclosure contemplatesany suitable combination of any suitable components, devices, or systemscarrying out any suitable steps of the method of FIG. 6.

The method may start, in some embodiments, at step 600, where one ormore packets may be received. For example, client 110 may have sent apacket. The packet may be destined for a node within data center 140.Client 110 may have sent the packet as part of a session with a servicebeing provided by a service provider that uses data center 140 to hostan application or service. The packet(s) may have a destination addressassociated with virtual machine VM1. The packet(s) may be received by arouter or a border node at data center 140, such as router 150 or borderelement 130.

At step 610, in some embodiments, a path identifier may be determinedfor the packet received at step 600. This step may be performed byborder element 130, router 150, or other suitable devices in data center140. As an example, the path identifier may be determined by examiningthe destination address (e.g., an Open Systems Interconnection (OSI)Layer 3 address such as the destination IP address) of the packetreceived at step 600. The path identifier may be associated with aservice provider associated with the destination IP address of thepacket received at step 600. As another example, the port on which thepacket was received (e.g., the ingress port) may be used to determinethe path identifier. The path identifier may be associated with aservice provider that is associated with one or more particular ports.Databases, tables, or other suitable information repositories may beused to determine the path identifier.

At step 620, in some embodiments, the path identifier determined at step610 may be inserted into the packet received at step 600. This step maybe performed by border element 130, router 150, or other suitabledevices in data center 140. For example, a header with the pathidentifier may be inserted into the packet (e.g., between OSI Layer 2and Layer 3 headers). As another example, a portion of a destination MACaddress may be modified and used as the path identifier. As anotherexample, the path identifier may be included in an Ethernet header ofthe packet (e.g., using bits reserved for VLAN stacking in the Ethernetheader).

At step 630, in some embodiments, a hardware identifier (e.g., an OSILayer 2 identifier) may be determined. This may be performed by router150. The hardware identifier determined at this step may be associatedwith the host associated with the destination IP address of the packetreceived at step 600. For example, if the packet received at step 600was associated with virtual machine VM1 and virtual machine VM1 ishosted on host 180, then the hardware identifier determined at step 630may be the MAC address of host 180. Other suitable hardware identifiersmay be used. Tables, databases, or other suitable informationrepositories may be used to determine the hardware identifier. Forexample, a routing table may be used at this depth that associates IPaddresses with corresponding MAC addresses.

At step 640, in some embodiments, the packet received at step 600 may besent to a switch. The switch may be coupled to the host associated withthe hardware identifier determined at step 630. For example, router 150may send the packet received at step 600 to switch 160 because thehardware identifier determined at step 630 was associated with host 180.

At step 650, in some embodiments, the path identifier is analyzed todetermine whether it is valid. This may be performed by switches 160 or170 or router 150. This may be performed by the switch receiving thepacket sent at step 640. For example, the path identifier may not bedetermined to be valid if the host or port associated with thedestination address of the packet received at step 600 has a differentpath identifier than the path identifier inserted at step 620. Asanother example, the entity sending the packet received at step 600 maybe associated with a different path identifier than the path identifierassociated with the host or port coupled to the switch that may receivethe packet. If the path identifier is determined not to be valid, thenstep 655 may be performed and the packet may be dropped. If the packetis determined to be valid, then step 660 may be performed and the packetmay be delivered to the host. After either step 655 or step 660 isperformed, the method may end.

The examples discussed above with respect to FIG. 6 illustrate howrouting may be performed in system 100. OSI Layer 2 routing may be usedin system 100 instead of, or in addition to, OSI Layer 3 routing. Forexample, an IP address is used as a logical identifier to identify ahost and the MAC address is used as a physical identifier to locate thehost in data center 140 in at least some of the examples discussed abovewith respect to FIGS. 1-6. In some embodiments, this may result in usingthe destination MAC address of a packet to route the packet to itsdestination instead of the destination IP address. The examplesdiscussed above with respect to FIG. 6 may also illustrate how networksegmentation may be performed in system 100. Service providers of datacenter 140 may be associated with separate path identifiers. Ports ofswitches in data center 140 (e.g., switches 160 and 170) may be coupledto separate service providers and the switches may include informationthat associates path identifiers with the ports of the switches. Forexample, ports of border element 130 may be associated with variousservice providers.

Advantages may be realized in one or more of the examples discussedabove with respect to FIGS. 1-6. For example, isolation of servicesand/or service providers in a data center may be achieved (e.g., OSILayer 2 isolation). This may prevent one service or vendor from beingable to send packets to another service or vendor in the data center.This may prevent one service or vendor from being able to observe IPaddresses associated with another service or vendor in the data center.As another example, the use of path identifiers may allow for a logicaldivision of a network in a data center to occur. This may allow fordividing hardware into groups. This may allow for dynamic reassignmentof hardware resources and associated efficiencies (e.g., being able topower off hardware when it is not in use).

While the various examples and embodiments discussed above use the OSImodel, the OSI model is only one example of a networking architecturethat may employ the techniques discussed herein. The teachings of thisdisclosure may be used with other suitable networking stacks, protocols,or architectures, such as the TCP/IP (Transmission ControlProtocol/Internet Protocol) model.

FIG. 7 illustrates an example computer system 700 suitable forimplementing one or more portions of particular embodiments. Althoughthe present disclosure describes and illustrates a particular computersystem 700 having particular components in a particular configuration,the present disclosure contemplates any suitable computer system havingany suitable components in any suitable configuration. Moreover,computer system 700 may have take any suitable physical form, such asfor example one or more integrated circuit (ICs), one or more printedcircuit boards (PCBs), one or more handheld or other devices (such asmobile telephones or PDAs), one or more personal computers, or one ormore super computers. Components discussed above with respect to FIGS.1-6 (e.g., client 110, network 120, border element 130, router 150,switches 160 and 170, and hosts 180-185) may be implemented using all ofthe components, or any appropriate combination of the components, ofcomputer system 700 described below.

Computer system 700 may have one or more input devices 702 (which mayinclude a keypad, keyboard, mouse, stylus, etc.), one or more outputdevices 704 (which may include one or more displays, one or morespeakers, one or more printers, etc.), one or more storage devices 706,and one or more storage medium 708. An input device 702 may be externalor internal to computer system 700. An output device 704 may be externalor internal to computer system 700. A storage device 706 may be externalor internal to computer system 700. A storage medium 708 may be externalor internal to computer system 700.

System bus 710 couples subsystems of computer system 700 to each other.Herein, reference to a bus encompasses one or more digital signal linesserving a common function. The present disclosure contemplates anysuitable system bus 710 including any suitable bus structures (such asone or more memory buses, one or more peripheral buses, one or more alocal buses, or a combination of the foregoing) having any suitable busarchitectures. Example bus architectures include, but are not limitedto, Industry Standard Architecture (ISA) bus, Enhanced ISA (EISA) bus,Micro Channel Architecture (MCA) bus, Video Electronics StandardsAssociation local (VLB) bus, Peripheral Component Interconnect (PCI)bus, PCI-Express bus (PCI-X), and Accelerated Graphics Port (AGP) bus.

Computer system 700 includes one or more processors 712 (or centralprocessing units (CPUs)). A processor 712 may contain a cache 714 fortemporary local storage of instructions, data, or computer addresses.Processors 712 are coupled to one or more storage devices, includingmemory 716. Memory 716 may include random access memory (RAM) 718 andread-only memory (ROM) 720. Data and instructions may transferbidirectionally between processors 712 and RAM 718. Data andinstructions may transfer unidirectionally to processors 712 from ROM720. RAM 718 and ROM 720 may include any suitable computer-readablestorage media. For example, aspects of this paragraph may be used toimplement routing data 132, 152, 162, and 172 as well as routing modules134, 154, 164, and 174.

Computer system 700 includes fixed storage 722 coupled bi-directionallyto processors 712. Fixed storage 722 may be coupled to processors 712via storage control unit 707. Fixed storage 722 may provide additionaldata storage capacity and may include any suitable computer-readablestorage media. Fixed storage 722 may store an operating system (OS) 724,one or more executables (EXECs) 726, one or more applications orprograms 728, data 730 and the like. Fixed storage 722 is typically asecondary storage medium (such as a hard disk) that is slower thanprimary storage. In appropriate cases, the information stored by fixedstorage 722 may be incorporated as virtual memory into memory 716. Forexample, aspects of this paragraph may be used to implement routing data132, 152, 162, and 172.

Processors 712 may be coupled to a variety of interfaces, such as, forexample, graphics control 732, video interface 734, input interface 736,output interface 737, and storage interface 738, which in turn may berespectively coupled to appropriate devices. Example input or outputdevices include, but are not limited to, video displays, track balls,mice, keyboards, microphones, touch-sensitive displays, transducer cardreaders, magnetic or paper tape readers, tablets, styli, voice orhandwriting recognizers, biometrics readers, or computer systems.Network interface 740 may couple processors 712 to another computersystem or to network 742. Network interface 740 may include wired,wireless, or any combination of wired and wireless components. Suchcomponents may include wired network cards, wireless network cards,radios, antennas, cables, or any other appropriate components. Withnetwork interface 740, processors 712 may receive or send informationfrom or to network 742 in the course of performing steps of particularembodiments. Particular embodiments may execute solely on processors712. Particular embodiments may execute on processors 712 and on one ormore remote processors operating together.

In a network environment, where computer system 700 is connected tonetwork 742, computer system 700 may communicate with other devicesconnected to network 742. Computer system 700 may communicate withnetwork 742 via network interface 740. For example, computer system 700may receive information (such as a request or a response from anotherdevice) from network 742 in the form of one or more incoming packets atnetwork interface 740 and memory 716 may store the incoming packets forsubsequent processing. Computer system 700 may send information (such asa request or a response to another device) to network 742 in the form ofone or more outgoing packets from network interface 740, which memory716 may store prior to being sent. Processors 712 may access an incomingor outgoing packet in memory 716 to process it, according to particularneeds.

Particular embodiments involve one or more computer-storage productsthat include one or more computer-readable storage media that embodysoftware for performing one or more steps of one or more processesdescribed or illustrated herein. In particular embodiments, one or moreportions of the media, the software, or both may be designed andmanufactured specifically to perform one or more steps of one or moreprocesses described or illustrated herein. In addition or as analternative, in particular embodiments, one or more portions of themedia, the software, or both may be generally available without designor manufacture specific to processes described or illustrated herein.Example computer-readable storage media include, but are not limited to,CDs (such as CD-ROMs), FPGAs, floppy disks, optical disks, hard disks,holographic storage devices, ICs (such as ASICs), magnetic tape, caches,PLDs, RAM devices, ROM devices, semiconductor memory devices, and othersuitable computer-readable storage media. In particular embodiments,software may be machine code which a compiler may generate or one ormore files containing higher-level code which a computer may executeusing an interpreter.

As an example and not by way of limitation, memory 716 may include oneor more computer-readable storage media embodying software and computersystem 700 may provide particular functionality described or illustratedherein as a result of processors 712 executing the software. Memory 716may store and processors 712 may execute the software. Memory 716 mayread the software from the computer-readable storage media in massstorage device 716 embodying the software or from one or more othersources via network interface 740. When executing the software,processors 712 may perform one or more steps of one or more processesdescribed or illustrated herein, which may include defining one or moredata structures for storage in memory 716 and modifying one or more ofthe data structures as directed by one or more portions the software,according to particular needs. In addition or as an alternative,computer system 700 may provide particular functionality described orillustrated herein as a result of logic hardwired or otherwise embodiedin a circuit, which may operate in place of or together with software toperform one or more steps of one or more processes described orillustrated herein. The present disclosure encompasses any suitablecombination of hardware and software, according to particular needs.

Herein, reference to a computer-readable non-transitory storage mediummay include a semiconductor-based or other integrated circuit (IC), suchas for example a field-programmable gate array (FPGA) or anapplication-specific IC (ASIC), a hard disk, an HDD, a hybrid hard drive(HHD), an optical disc, an optical disc drive (ODD), a magneto-opticaldisc, a magneto-optical drive, a floppy disk, a floppy disk drive (FDD),magnetic tape, a holographic storage medium, a solid-state drive (SSD),a RAM-drive, a SECURE DIGITAL card, a SECURE DIGITAL drive, anothersuitable medium, or a suitable combination of these, where appropriate.A computer-readable non-transitory storage medium may be volatile,non-volatile, or a combination of volatile and non-volatile, whereappropriate.

Herein, “or” is inclusive and not exclusive, unless expressly indicatedotherwise or indicated otherwise by context. Therefore, herein, “A or B”means “A, B, or both,” unless expressly indicated otherwise or indicatedotherwise by context. Moreover, “and” is both joint and several, unlessexpressly indicated otherwise or indicated otherwise by context.Therefore, herein, “A and B” means “A and B, jointly or severally,”unless expressly indicated otherwise or indicated otherwise by context.

This disclosure encompasses all changes, substitutions, variations,alterations, and modifications to the example embodiments herein that aperson having ordinary skill in the art would comprehend. Moreover,reference in the appended claims to an apparatus or system or acomponent of an apparatus or system being adapted to, arranged to,capable of, configured to, enabled to, operable to, or operative toperform a particular function encompasses that apparatus, system,component, whether or not it or that particular function is activated,turned on, or unlocked, as long as that apparatus, system, or componentis so adapted, arranged, capable, configured, enabled, operable, oroperative.

What is claimed is:
 1. A method executed by at least one processorcomprising: receiving, at a first network element, a first packet sentby a first node, the packet comprising a first Layer 3 source address, afirst Layer 3 destination address, a first Layer 2 source hardwareidentifier, a first Layer 2 destination hardware identifier, and a firstpath identifier, the first path identifier situated between a Layer 2header of the first packet and a Layer 3 header of the first packet; inresponse to receiving the first packet, automatically determining afirst port of the first network element associated with a second node,the second node associated with the first Layer 2 destination hardwareidentifier; automatically determining a second path identifier based onthe first port; automatically preventing the first packet from beingdelivered to the second node associated with the first Layer 2destination hardware identifier in response to determining that thefirst path identifier and the second path identifier are different. 2.The method of claim 1, wherein the first network element comprises aswitch.
 3. The method of claim 1, further comprising: determining, at asecond network element, the first path identifier based on an ingressport of the second network element configured to receive the firstpacket; and inserting, by the second network element, the first pathidentifier into the first packet.
 4. The method of claim 3, whereininserting the first path identifier into the first packet comprisesadding a header to the first packet, the header comprising the firstpath identifier.
 5. The method of claim 1, further comprising:receiving, at the first network element, a second packet after receivingthe first packet, the second packet comprising a second Layer 3 sourceaddress, a second Layer 3 destination address, a second Layer 2 sourcehardware identifier, a second Layer 2 destination hardware identifier,and a third path identifier; automatically determining a fourth pathidentifier based on a second port of the first network elementassociated with the second Layer 2 destination hardware identifier;automatically causing the first packet to be delivered to a third nodeassociated with the second Layer 2 destination hardware identifier inresponse to determining that the third path identifier and the fourthpath identifier are the same.
 6. The method of claim 1, wherein thefirst Layer 3 destination address is an Internet Protocol (IP) addressand the second Layer 2 hardware identifier is a Media Access Control(MAC) address.
 7. The method of claim 1, wherein the first pathidentifier is associated with a first service provider and the secondpath identifier is associated with a second service provider, the firstservice provider providing a first service using a first data center,the second service provider providing a second service using the firstdata center.
 8. Non-transitory computer-readable media comprisinginstructions that, when executed by a processor, are configured to:receive, at a first network element, a first packet sent by a firstnode, the packet comprising a first Layer 3 source address, a firstLayer 3 destination address, a first Layer 2 source hardware identifier,a first Layer 2 destination hardware identifier, and a first pathidentifier, the first path identifier situated between a Layer 2 headerof the first packet and a Layer 3 header of the first packet; inresponse to receiving the first packet, automatically determine a firstport of the first network element associated with a second node, thesecond node associated with the first Layer 2 destination hardwareidentifier; automatically determine a second path identifier based onthe first port; automatically prevent the first packet from beingdelivered to the second node associated with the first Layer 2destination hardware identifier in response to determining that thefirst path identifier and the second path identifier are different. 9.The media of claim 8, wherein the first network element comprises aswitch.
 10. The media of claim 8, wherein the instructions are furtherconfigured to: determine, at a second network element, the first pathidentifier based on an ingress port of the second network elementconfigured to receive the first packet; and insert, by the secondnetwork element, the first path identifier into the first packet. 11.The media of claim 10, wherein the instructions are configured to insertthe first path identifier into the first packet by adding a header tothe first packet, the header comprising the first path identifier. 12.The media of claim 8, wherein the instructions are further configuredto: receive, at the first network element, a second packet afterreceiving the first packet, the second packet comprising a second Layer3 source address, a second Layer 3 destination address, a second Layer 2source hardware identifier, a second Layer 2 destination hardwareidentifier, and a third path identifier; automatically determine afourth path identifier based on a second port of the first networkelement associated with the second Layer 2 destination hardwareidentifier; automatically cause the first packet to be delivered to athird node associated with the second Layer 2 destination hardwareidentifier in response to determining that the third path identifier andthe fourth path identifier are the same.
 13. The media of claim 8,wherein the first Layer 3 destination address is an Internet Protocol(IP) address and the second Layer 2 hardware identifier is a MediaAccess Control (MAC) address.
 14. The media of claim 8, wherein thefirst path identifier is associated with a first service provider andthe second path identifier is associated with a second service provider,the first service provider providing a first service using a first datacenter, the second service provider providing a second service using thefirst data center.
 15. A system comprising: a first network elementconfigured to receive a first packet sent by a first node, the packetcomprising a first Layer 3 source address, a first Layer 3 destinationaddress, a first Layer 2 source hardware identifier, a first Layer 2destination hardware identifier, and a first path identifier, the firstpath identifier situated between a Layer 2 header of the first packetand a Layer 3 header of the first packet; wherein the first networkelement comprises a processor configured to: in response to receivingthe first packet, automatically determine a first port of the firstnetwork element associated with a second node, the second nodeassociated with the first Layer 2 destination hardware identifier;automatically determine a second path identifier based on the firstport; and automatically prevent the first packet from being delivered tothe second node associated with the first Layer 2 destination hardwareidentifier in response to determining that the first path identifier andthe second path identifier are different.
 16. The system of claim 15further comprising: a second network element comprising an ingress portconfigured to receive the first packet, the second network elementconfigured to: determine the first path identifier based on the ingressport; and insert, by the second network element, the first pathidentifier into the first packet.
 17. The system of claim 16, whereinthe second network element is configured to insert the first pathidentifier into the first packet by adding a header to the first packet,the header comprising the first path identifier.
 18. The system of claim15, wherein: the first network element comprises a second port and isfurther configured to receive a second packet after receiving the firstpacket, the second packet comprising a second Layer 3 source address, asecond Layer 3 destination address, a second Layer 2 source hardwareidentifier, a second Layer 2 destination hardware identifier, and athird path identifier; and the processor is further configured to:automatically determine a fourth path identifier based on the secondport being associated with the second Layer 2 destination hardwareidentifier; automatically cause the first packet to be delivered to athird node associated with the second Layer 2 destination hardwareidentifier in response to determining that the third path identifier andthe fourth path identifier are the same.
 19. The system of claim 15,wherein the first Layer 3 destination address is an Internet Protocol(IP) address and the second Layer 2 hardware identifier is a MediaAccess Control (MAC) address.
 20. The system of claim 15, wherein thefirst path identifier is associated with a first service provider andthe second path identifier is associated with a second service provider,the first service provider providing a first service using a first datacenter, the second service provider providing a second service using thefirst data center.